Method of making cellular resin material



Patented Feb. is, 1949 mrrnon or MAKING CELLULAR. nnsm Louis E. marinrs, Ind., wSt'ates Rubber Company,

signer to United New York, N. Y., a

corporation of New Jersey I No Drawing. mum... February 2, 1945,

Serial uas'zsbzs '0 Claims. (01. 200-454) This invention relates to amethod of making a cellular or expanded resin material, that is formedfrom a whipped up'or expanded 100 per cent polymerizable thermosettingresin."

There are now available two distinct types of polymerizablethermosetting resins marketed in liquid or semi-liquid form. The firsttype includes such synthetic resins as urea and phenol formaldehydewhich when polymerized, or when they undergo a condensation reaction,produce a,

by-product such as water; these resins can be about 90 per centpolymerized, are soluble in alcohol or some organic solvent and alwaysthrow on some by-product upon completion of the polymerization reaction..The second type of synthetic resins can be substantially 100'per centpolymerized and contains no volatile non-polymerizable solvent. Thepresent invention is-concemed with this second type of resins.

The earlier efforts made by me to produce a cellular or expandedmaterial from this second type of resins by expanding the liquidv orsemiliquid resin and then setting it to a cellular hardened condition,were not successful because after the resin'material is whipped up orexpanded into a foamy mass it has to be heat-cured to polymerize orharden the resin, and the foamy mass would fall or settle to a'compactsolid under the action of the heat.

As a result of these unsuccessful early efforts to produce a cellularresin material from this type of resins it became apparent that thefoamy mass would have to be made more stable so that it would retain itscellular condition during the curing or setting period.

I have found that if a chemical blowing agent and a small amount of zincstearate, or other metal stearate, such as lead. sodium, calcium orbarium stearate, are added to a resinous mix of the above mentioned 100per cent polymerizable type of resin, and the mixture is then whipped toform a foamy mass, the metal stearate acts as a foam stabilizer andcauses the foamy mass to remain expanded while it is being heat-cured toa cellular hard mass.

The present invention relates to a method of making a rigid cellularmaterial from thermosetting resins of the above mentioned class of 100per cent polymerizable resins and more particularly to a method ofstabilizing the foamed resin so that it will not ialldurlng the curingperiod. These resins are formed of liquid or semi-liouid polymerizablecomponents which polymerize, together, or interpolymerize in what isknown as the oil phase, without splitting off by-products, e. g., water,to form, eventually hard resins.

Thisclass of res ns may be further described as those resins produced bythe interpolymerization of unsaturated alkyd resins with'monoen'ic zcompounds having a single terminal ethylenic group CH2=C To this classof resins belong the resins represented by the polyethyleneglycol-maleate-styrene copolymer resins covered by the Ellis U. 8.Patents Nos. 2,255,313 and 2,195,362

.and the American Cyanamid Co. British Patents 540,167 and 540,168. Asshown 'in the Ellis Patent No. 2,255,313, these resins may be formed byreacting an ethylene-alpha-beta dicarboxylic acid with a glycol, in suchproportions that there are present in the reacting mixture about onecarboxyl group in such unsaturated acid to one hydroxyl group in suchglycol, to an advanced stage of esteriflcation but short of becomingcompletely insoluble and infusible, until a product of low acid numberis produced which is soluble in a liquid monomeric unsaturatedpolymerizable compound containing an ethylenic linkage, incorporatingthe product of such esterification with a liquid monomericunsaturatedpolymerizable compound containing an ethylenic linkage, and thereaftersubjecting said solution to conjoint polymerization. These resins hardento form tough, non-cracking surfaces.

A good practical composition for making a hard cellular .resin. such ascontemplated by the' present invention, from a liquid or semi-liquidresin of the type above described is produced by the following formula:1

. Grams Resin (100% polymerizable such as described above) -s 100Benzoyl peroxide (catalyzer) 1 Tertiary butyl hydroperoxide (cataiyzerbooster) e 1 Blowing agent (foaming agent) 20-30 Acetic acid (foamingagentactivator) 1-5 Phenyl hydrazine (gelling agent) .05 -0.2

Blowing agent comprising zinc stearate, sodium bicarbonate and water inthe proportions of one to two to six by weight.

Theinnredlents are listed inthe order in which they shouldbe added tothe mix. The'resin is catalyzed by the addition of the benzoyl peroxideand is aerated with a high speed mixer. The

zinc a e. sodium bicarbonate and water are.

mixed together and then added to the aeratedresin and, whipped.therewith until dispersion is complete and a light foamy mass is formed.Any of the stearates above mentioned may be used but zinc stearate ispreferred.

' Phenyl hydrazine acts as a gelling agent for the foam and is usually aded with the acetic acid just before casting. v The foam will begin I togelwith n two 'or three m nutes after the phenyl hydrazine has beenadded, and will be completely gelled within five or six minutes. This iscontrolled by the amount of phenyl hydrazine added, and if it is foundthat-the foam is gelling too fast, the amount of gelling agent may becut down.

Tertiary butyl hydroperoxide is not essential to make the resinpolymerize, but it speeds up same and a cover is applied whereupon it isready for curing, or this foamy resinous mass may be deposited on acontinuously moving belt and gelled thereupon.

The curing of the mix of the above formula may be carried out at atemperature of 230 to 260 F. for from thirty minutes to one hour. Thevariable here is due to changes in the recipe. When the belt method isused the foam material gels on the traveling belt and is partly driedthereupon by passing through a hot air oven or high frequencyalternating current field. It is then placed in an oven at about 250 F.for 80 to 45 minutes for final cure. I

The specific gravity of the cellular or expanded material of the presentinvention may be varied by varying the amount of air whipped with theresin and also by varying the amount of blowin agent used. Using a 100per cent polymerizable resin such as is described above a cellular masshas been produced that weighed as little as three or four pounds percubic foot. Tests show that it is possible by practicing the presentmethod to produce cellular material having a specific grav- 0 ity of .06to .0'7, and sumcient hardness and rigidity to support a load of about100 pounds per square inch. As the specific gravity increases to about.175 the material is capable of supporting 200 pounds per square inch.Urea or phenol formaldehyde foam is only about one-third to one-half asstrong as this.

The present cellular resin material has excellent resistance to water.It also has good dielectric properties, and can be used in radarhousings and similar fields. The material also has excellent resistanceto all types of organic solvents; including alcohols, esters,chlorinated hydrocarbons, ethers, gasoline, aromatic hydrocarbons andetc. Furthermore it burns slowly.

The physical and chemical properties of this rigid cellular materialmake it well adapted for use as wing liners in airplanes, as a spacer ina sandwich construction for radar equipment, in aircraft construction inwhich it is sandwiched between structural sheets'of aluminum, plywood orthe like to give high strength andresistance to bending with a minimumof weight.' It is also well adapted for use as a sound deadener andthermal insulator. v

This material can be easily cut and sawed into any desired shape, andsince it is produced by a combined whipping and chemical blowing actiona great number of the cells will be spherical in shape which is a goodconstruction for strength and heat insulating properties.

.Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. The method of making a rigid cellular resin material which comprisesforming a ,mixture I a 4 of a copolymerizable mix of a monoenic compoundhaving a single terminal ethylenic group CKa= withan unsaturated alkydresin which is the reaction product of an ethylenic-alphabetadicarboxylic acid with a glycol, a polymerization catalyst, a chemicalblowing agent, and a metal stearate as a foam stabilizer, whipping themixture to form a foamy mass, and then heat-curing said foamy mass to acellular hardened condition. a

2. The method of making a rigid cellular resin material which comprisesforming a mixture of a copolymerizable mix -of a monoenic compoundhaving a single terminal ethylenic group CH2=C with an unsaturated alkydresin which is the reaction'product of an ethylenic-alphabetadicarboxylic acid with a glycol, a polymer. ization catalyst, a chemicalblowing agent, and zinc stearate as a foam stabilizer, whipping themixture to form a foamy mass, and then heatcuring said foamy mass to acellular hardened condition.

3. The method of making a rigid cellular resin material which comprisesforming a mixture of a copolymerizable mix of a monoenic compound havinga single terminal ethylenic group CH2=C with an unsaturated alkyd resinwhich is the reaction product of an ethylenic-alphabeta dicarboxylicacid with a glycol, a polymerization catalyst. a chemical blowing agent,and

a metal stearate as a foam stabilizer, whipping the mixture to form afoamy mass, adding phenyl hydrazine to said foamy mass, and thenheatcuring said mass to a cellular hardened condi- 5 tion.

4. The method of making a rigid cellular resin material which comprisescommingling a copolymerizabie mix of a monoenic compound having a singleterminal ethylenic group CH==C with an unsaturated alkyd resin which isthe reaction product of an ethylenic-alpha-beta dicarboxylic acid with aglycol, with benzoyl peroxide as a polymerization catalyst, admixing amixture of zinc stearate', sodium bicarbonate and water with theresulting mixture, whipping the resulting mixtureto a foamy mass. addingphenyl hydrazine and acetic acid to the resulting foamy mass, and thenheat-curing said mass to a cellular hardened condition.

5. The method of making a rigid cellular resin material which comprisesforming a mixture of a copolymerizable mix of a polyethylene glycolmaleate and styrene, a polymerization catalyst. a chemical blowingagent, and a metal stearate as a foam stabilizer, whipping the mixtureto form a foamy mass, and then heat-curing said foamy mass to a cellularhardened condition.

I REFERENCES CITED The following references are of record in the file ofthis patent:

FOREIGN PATENTS Number Country Date 831,227 GreatBritain -Jun e 24, 1930

